Food Cravings and what those foods do to your brain!

Ever find yourself staring at that delicious chocolate cake or pumpkin pie on the shelf and with your mouth watering just at the sight of it? Then you know how craving food feels like.

Scientists define food craving as the intense desire for a very specific food and your willingness to go out of your way to receive it. A lot of us blame ourselves for giving into those cravings “letting go” by indulging into something either sweet or very fatty, but there are many scientific facts that now allow us to understand why those foods are so tempting.

Many questions may arise when you think about food craving and I will attempt to answer a couple with this post, starting with: What types of foods do we crave and why?

Many of us think of craving as the desire for something sweet, but scientists at Tufts University did a wide study, where they found that even though sugary foods are preferred, fats are not left behind. The craving for a specific type of food differs on a personal basis, but we mainly tend to go for foods that are very calorie dense and tend to go for a combination of carbohydrate and fat rich food. An interesting thing that those researchers also found is that the craving intensity did not depend on body mass index of the people tested. Lean people experienced just as much craving as obese ones, but the obese ones would need bigger amount of food to satiate that craving.

So why do we have those cravings is the next most logical question? The only theory that holds strong logic in this case is derived from our evolutionary history. Any species needs nutrition to survive and through the years nutrition has not been as readily available as it is now. Thus, it would be more beneficial for our predecessors to find food that is highly packed with those vital calories they would need. So in the idea of “survival of the fittest”, the fit specimen would be the ones able to find enough calories to survive, thus the ones that seek them most avidly are the ones that find them. On the other hand, that doesn’t mean that you can blame your ancestors for all your cravings, it’s partly your fault!

Now that we know that we can partly blame evolution this leads us to two more questions: What exactly happens that causes us to crave and why are we in part to blame for cravings?

Researchers at Johns Hopkins Medical School have found that there are specific centers that light up in the brain on a functional MRI (magnetic resonance imaging) when people think about foods they crave. The fact that those sections light up, shows they are activated. The more interesting thing is that those sections don’t activate when we think about low calorie food, but also that those are the same parts of the brain connected to drug addiction.

The amygdale, hypocampus and nucleus accumbens are strongly associated centers of pleasure. Those are the same places that drugs activate and those are the same places activated by the sight or thought of craved foods. Through those images the researchers also found something even more fascinating: when lean people consume craved food those sections light up more strongly than in obese people. Lesson learned – leaner people experience more satisfaction from the food than obese people, who have to consume more to receive the same satisfaction.

So why should we in part blame ourselves for our cravings? The more often you indulge on these “craved” foods you train your brain to get accustomed to them, a process called “sensitization.” The more accustomed your brain is, the less satisfaction you receive from eating that food you craved. The less satisfaction you get the bigger amount you crave. It is a vicious cycle that leads into obesity and depression very fast. Food addiction is real and it is not to be undermined.

To leave you on a positive note all of this is to just remind you that “craving” food is absolutely normal and 96% of people experience it. The difference is that if you indulge on that craving frequently it will become stronger. The good side is that like any addiction it can be overcome. As long as you stick to a good diet, it is estimated that you can go back to the same amount of craving as a “lean” person within 3-6 months. Hope that helps!

Sources:

Beaver, J., et. al. “Individual Differences in Reward Drive Predict Neural Responses to Images of Food.” Journal of Neuroscience. Vol. 26(19) Pg:5160 –5166. May 10, 2006

Pelchat, M. et. al. “Images of desire: food-craving activation during fMRI.” NeuroImage. Vol. 23. Pg 1486-1493. 2004

Bryant, R., Dundes, L. “Fast food perceptions: A pilot study of college students in Spain and the United States.” Apetite. Vol 51. Pg. 327-330. 2008

Gilhooly C., et. al. “Food cravings and energy regulation: the characteristics of craved foods and their relationship with eating behaviors and weight change during 6 months of dietary energy restriction.” International Journal of Obesity. Vol 12. Pg 1849-58. 2007

Tufts University, Health Sciences. “Links Between Food Cravings, Types Of Cravings, And Weight Management.” ScienceDaily, 18 Jul. 2007. Web. 24 Nov. 2011


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About eliasoziolor

My name is Elias and I am a senior at DePauw University double majoring in Biology and Biochemistry. I was born and raised in the small town of Razgrad in Bulgaria, though I pursued my high school education in the capital, Sofia. I have been interested in science since I was a kid. Being a part of the math club in middle school and picking physics electives in high school I tried to always progress in various scientific fields. At DePauw I became part of the Science Research Fellows program as a lateral entry, which gave me the opportunity to pursue various projects including amphibian immunology, aquatic ecology and molecular biology. My latest project was at a joint program between Harvard Medical School and Massachusetts General Hospital where I studied inflammatory signaling in human intestinal epithelial cells. DePauw also has given me the opportunity to pursue a wide variety of extracurricular activities including being a First-Year Residence Assistant, Prindle Ethics Intern, DJ at the local radio and an Immunolgy tutor. All my experiences made me interested at how science explains the world around and I hope to make you as curious and excited about science through my posts in this blog.

8 thoughts on “Food Cravings and what those foods do to your brain!

  1. This was a really interesting post. It was informative and really related to a common social/personal issue that affects all people. I thought the point about lean people having greater responses to thinking about food they crave was particularly interesting. I liked how the author organized the post, starting with commonly asked questions- “why do we crave sweets?/why do most people have a sweet tooth?” and moved to the evolutionary reasons behind these feelings before moving into more applicable reasons that we, personally, can control. One piece of the post I had an issue with was the part that referenced obesity leading to depression. I would like to see this referenced specifically as it is kind of a large jump from a physical health issue to a mental health problem. This trend is not always the case and seems to be a presumption.

  2. Hey,

    I’m sorry i didn’t explain that completely. There is a couple of articles that suggest that and there has been multiple research projects that are leading to stronger evidence to suggest that obesity and depression are strongly linked. One of the major ideas is that as you are exercising this pleasure center by indulging into these “craved” foods, your pleasure center is becoming sensitized to that stimulus, so you are getting less pleasure from eating them. Therefore when those craved foods have been a comfort before, now they don’t bring you pleasure. One cause of depression can be if your pleasure centers in the brain are desensitized and the serotonin that usually brings you pleasure from normal things is not enough because you have been numbed by all the serotonin that has been released by craved foods.
    Another idea is that adipocytes, or the specialized cells of your organism that store fat, release the inflammatory cytokine – interferon 1 beta. The interesting thing is that this same cytokine (hormone of the immune system) is capable of crossing the blood-brain barrier and is shown to cause depression when it reaches the brain. Thus, with a higher quantity of adipose tissue will be producing more of that cytokine and therefore have a higher likelihood of being depressed.
    I’m sorry I didn’t explain that as thoroughly.
    Here are a couple of articles that talk on both of these hypotheses.
    Thanks for the question.

    -Elias

    Wurthman RJ, Wurthman JJ. “Brain serotonin, carbohydrate-craving, obesity and depression.” Obesity Research. Vol. 4. 477-480. 1995

    Stunkard, A. et al. “Depression and Obesity.” Society of Biological Psychiatry. 54:330–337. 2003

    Onyike, C. et al. “Is Obesity Associated with Major Depression? Results from the Third National
    Health and Nutrition Examination Survey.” American Journal of Epidemiology. Vol. 158, No. 12. 2003

    Thomas, AJ. et al. “ Increase in interleukin-1beta in later-life depression.” The American Journal of Psychiatry. [2005, 162(1):175-7]

    Fain et al. “Comparison of the Release of Adipokines by Adipose Tissue, Adipose Tissue Matrix, and Adipocytes from Visceral and Subcutaneous Abdominal Adipose Tissues of Obese Humans.” Endocrinology. May 1, 2004 vol. 145 no. 5 2273-2282

  3. I must say that I loved this post!
    I have a major sweet tooth and am pretty sure that I am an addict. Even just the thought of a sweet can trigger a craving ( I would be the top dog in prehistoric times). After reading this post, however, I decided that I want to try and break this bad habit (depression is no joke). Upon doing some research, I found this cool book “Overcoming overeating: How to break the diet/binge cycle and live a healthier, more satisfying life”. Though I couldn’t read all of it (google book only gives you part of the content), I realized that cravings and the subsequent eating can be attributed to psychological hunger as opposed to physiological hunger. In order to overcome this addiction you have to reprogram yourself to eat when you are hungry as opposed to when it sounds good or suits you.
    So thanks to this post, I’m going to start off on a new foot with my sweets.

  4. I thought that the idea that obese/heavier people need more of the food that they are craving to feel satisfied compared to lean people was really interesting. It also got me thinking about how we sense satiety. I found a post on the Harvard Health blog (http://www.health.harvard.edu/blog/why-eating-slowly-may-help-you-feel-full-faster-20101019605) that talked a little bit about this. The post basically stated that sensing fullness has to do with both your stomach and your brain. The stomach contains stretch receptors that then transmit signals to the brain via the vagus nerve. The post also talked about two hormones that are released during the eating process. Cholecystokinin, which is released by the small intestine, and leptin, which is released by adipose cells, are both involved in conveying to the brain what the bodies needs are based on energy stores and satiety levels. In terms of dieting, the post recommends that people who are seeking to lose weight eat slowly so that the body, specifically the brain, has time to receive and interpret these nervous and hormonal signals from the brain. To me, it made sense that eating slower would allow you to better realize when you are full, and it also gives merit to the popular diet advice that you should take your time while you are eating.

  5. One question I had was about people’s response to the brain signals during a craving. Are there other factors that go into fighting a craving for sweet or fatty food other than the connection between obesity and less satisfaction when eating the food. When I tried to find out more information, I could only find dieting sites that gave the “top 10 ways to fight food cravings.” These sites did not have any scientific data like you presented, only tips about replacing the craved foods with healthier options, etc. I was wondering if you came across any other scientific information during your research.

    Also, what about when people crave healthy foods such as fruits and vegetables? Your post only addresses craving unhealthy foods.

  6. I really liked this article and it made me think of a kind of cravings that seem to be frequently shown in movies and television shows to add humor: pregnancy cravings. I thought that the explanation of survival of the fittest for cravings seemed like a good one for pregnancy as well, but the one thing that didn’t seem to align was the frequent occurrence of women craving things that they wouldn’t normally eat and end up having an aversion to later. It turns out that during pregnancy your sense of taste and smell change due to the changes in hormones and that is why they believe that some women begin craving unusual food. But beyond unusual foods, I found some articles that showed that there were even cases of women craving non-food items. These doctors have not been able to explain but some believe that it is due to a deficiency in iron.

    http://www.epigee.org/pregnant_diet.html
    http://www.americanpregnancy.org/pregnancyhealth/unusualcravingspica.html

  7. The idea that the severity of cravings are basically dependent on how much an individual gives in to them really stuck with me after I read this article. It makes a lot of sense though if I think about how once I give in to that handful of cookies or one doughnut in the morning, it is much more difficult to deny a dessert the next time. I always thought this had more to do with willpower and rationalizing that just one more would not hurt; however, I can accept that as I continue to eat more I will rationalize a larger amount. As soon as I am on a healthy diet I do not eat, or even want to eat, more than a cookie because it quickly becomes overwhelming.

    This made me think more about how diets in general would affect these cravings, not just lean versus obese body types. I found a study on obese individuals who committed to either a low carbohydrate or low fat diet for two years. Researchers recorded their appetite; cravings for specific types of foods; and preferences for high-sugar, high-carbohydrate, and low-carbohydrate/high-protein foods. It was discovered that both sample groups had significant decreases in craving for whichever respective major nutrient from which they abstained. The low carbohydrate sample group were also less bothered by hunger in general. I thought this was really interesting because it shows that specific cravings can be reduced by certain diets.

    http://www.nature.com/oby/journal/v19/n10/full/oby201162a.html?WT.ec_id=OBY-201110

  8. I also was curious about pregnancy craving when I read this article. I have actually known people and have seen people on television who crave non-food items like chalk, metal, plastic, fabric, etc. Could this being something in the brain going hay-wire? I did a little research and found out that this is actually a disease called “Pica,” in which patients constantly crave and compulsively ingest nonfood substances. I found an article about a case-control study done in France that tried to show that iron deficiency is, indeed, very heavily correlated with the cravings. They were able to find that those with iron deficiency had unexpectedly high frequencies of pica. They were also able to determine that it has something to do with ethnic and cultural differences.

    http://www.idpas.org/pdf/4200.pdf

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